Mr Gertler has used an array of offshore companies to amass his interests in the DRC. The BVI-registered vehicle he used for the Katanga Mining transactions with Glencore was called Lora Enterprises Limited. Its name would crop up again, last year, in a corruption scandal that has humbled one of New York’s leading hedge funds.

In September, Och-Ziff, a fund with $39bn under management, paid $413m in fines to US civil and criminal authorities after admitting complicity in bribery in five African countries. The fund and the authorities released an agreed account of Och-Ziff’s misconduct. The section on the DRC made uncomfortable reading for Glencore.

The US prosecutors’ account states that, between 2005 and 2015, an “Israeli businessman . . . paid more than one hundred million US dollars in bribes to obtain special access to and preferential prices for opportunities in” Congo’s mining sector. It goes on to describe loans from Och-Ziff to the Israeli that were allegedly used, in part, to pay bribes.

The descriptions of two of the unnamed recipients of the alleged bribes indicate they were President Joseph Kabila and his late right-hand-man, Augustin Katumba Mwanke.

The description of the Israeli businessman’s dealings makes it clear the source of the alleged bribes is Mr Gertler. His representatives said: “We dispute all accusations of wrongdoing in any of our dealings in the DRC including those with Och-Ziff . . . We dispute any allegation of bribery.” The DRC government also rejected the allegations and praised Mr Gertler’s commitment to the country.

According to the Och-Ziff settlement documents, in November 2010, Michael Cohen, the London-based executive who ran the fund’s African operations, emailed a subordinate to say that “[Mr Gertler] has asked for a margin loan on katanga shares which want u to handle”. Mr Cohen, who denies US civil charges of corruption, was referring to the significant minority shareholding in Katanga Mining that Glencore’s $45m loan had enabled Mr Gertler to maintain.

Within two weeks, Och-Ziff had sent $110m in credit via the Cayman Islands to Mr Gertler’s Lora Enterprises Limited. The same day, Lora repaid Glencore’s $45m loan, plus interest. Then, it appears from the Och-Ziff settlement statement, Mr Gertler is alleged to have used some of the remaining money for bribes, including four payments in eight days totalling $7m to “DRC Official 1” — Mr Kabila.

Glencore stresses that, unlike other mining companies, it did not secure its entry into the DRC’s vast copper belt through a deal with Mr Gertler, but rather ended up in business alongside him when they independently acquired interests in some of the country’s mining assets. The Swiss group accepts that it has helped Mr Gertler financially, but says its involvement in a string of offshore transactions that culminated in the alleged bribery by the Israeli ended well before any illicit payments were made.

Glencore said: “The loan that Glencore made to Lora was used by Lora in 2009 to fund its participation in a convertible loan to Katanga, which was ultimately exchanged for shares in Katanga. The loan was on commercial terms and was fully secured over the Katanga shares. The loan was fully repaid to Glencore in 2010, at which point the security was released. Following the release of the Glencore security, Lora was free to dispose of the Katanga shares or to use them as security for further financing.”

A spokesman for Fleurette, Mr Gertler’s group, declined to discuss the transactions involving Lora but said that, because the company had bought its initial Katanga Mining shares before their value collapsed, it had suffered an overall $190m loss on its dealings in the stock. He added the two mining operations in which Fleurette was an erstwhile shareholder with Glencore “have generated $3bn in tax for the people of the DRC”.

Last month, Glencore said it had bought Fleurette’s 10 per cent stake in Katanga Mining. Glencore also purchased Fleurette’s 31 per cent stake in the other shared DRC copper mining venture, called Mutanda Mining.

The stakes were valued at $960m, but Glencore deducted the value of loans it had issued to Fleurette to help finance the two copper mines’ development, plus interest. This meant Mr Gertler received $534m in cash from Glencore.

Glencore now owns all of Mutanda Mining, and 86 per cent of Katanga Mining, and its increased ownership of the two assets gives the group greater exposure to copper, which is viewed as one of the most attractive commodities in the mining industry.

Glencore has not entirely cut its ties with Mr Gertler. He will continue to receive tens of millions of dollars in royalties each year from Glencore’s copper deposits under a deal with Gecamines, the DRC’s state-controlled mining company. However, his royalty rights at Katanga Mining are unlikely to bring in much: they expire in 2019, not long after the asset, currently closed for an upgrade, is due to restart operations.Glencore is one of the world’s bigger copper miners

Glencore may be best known as a commodity trader, but the Swiss group is also one of the world’s biggest producers of copper, a key industrial metal.

Last year, Glencore’s copper mines in Africa, Australia and Latin America generated about one-third of the group’s earnings before interest, tax, depreciation and amortisation — making them the single biggest source of profit.

Copper is used in everything from household wiring to power grids, and is closely followed by the financial community because of its status as a barometer of the global economy.

Including its share of joint ventures, Glencore expects to produce up to 1.4m tonnes of copper this year, about 6 per cent of global output.

That figure will rise in 2018 when the company restores production at two key copper assets: its Katanga Mining operations in the DRC and deposits at Mopani in Zambia.

The two assets were taken offline amid the commodity slump in 2015 that unleashed a debt crisis at Glencore, and these African operations are currently undergoing efficiency overhauls.

Richard Wilson, of industry consultants Wood Mackenzie, says Glencore’s Katanga mining operations in particular will be a “transformed asset”, capable of producing 300,000 tonnes of copper each year, once a new $437m processing system is up and running.

Glencore will be able to extract more cobalt, a byproduct of copper mining that is used in the batteries that power mobile phones and electric cars. “Glencore have got themselves a long life, low cost mine,” says Mr Wilson.